The invention relates to a connection device with which at least one electric hollow conductor of an electric machine can be connected to an electrical energy source. The invention also relates to an electric machine with at least one such connection device.
In order to provide a particularly high power with an electric machine such as an electric motor, relative to its weight, it is sought to achieve a greatest possible current density in the electrically conducting material of windings of the electric motor. However such a high current density is associated with heat losses, which are dissipated with elaborate measures to prevent damage to the electric motor.
For the purpose of cooling for example cooling plates can be provided, which are impinged with cooling air. In addition other types of air cooling and also cooling with liquids are known from the state of the art. In electric motors known from the state of the art oftentimes heat is emitted via an electrical insulation from wires used in the windings of the electric motor. This is associated with a comparatively low efficiency because in most cases the electric insulation is also a good heat insulator.
It is also known from the state of the art to configure electrical conductors, which are arranged in grooves of a laminated core of the stator of an electric machine and form windings of the stator, as hollow conductors. Through these hollow conductors a coolant can be conducted in order to dissipate the heat loss. The use of electric hollow conductors through which a coolant can flow is for example known from power plant construction, for example when the electric machine is constructed as a turbo generator. However, the diameters of the hollow conductors used in this case are significant, i.e., in the range of more than 30 mm. However for non-stationary electric machines as they may for example be used in a motor vehicle, the use of coils made of hollow conductors through which a coolant can be conducted is relatively difficult. This is because the connected systems require a significant amount of mounting space and result in significant additional weight.